Home composting is a practical and sustainable approach for the management of organic waste generated in the home and agricultural production that contributes to both organic waste management and soil fertility enhancement. In the northern mountainous regions of Vietnam, smallholder farmers face limited adoption of sustainable waste management practices due to behavioral constraints, limited technical knowledge, and resource constraints affecting agricultural productivity.  This study applies and extends the Theory of Planned Behavior (TPB) by integrating behavioral and contextual determinants to examine home composting adoption among smallholder farmers in rural Vietnam. Principal Component Analysis (PCA) was used to reduce and structure latent behavioral constructs, while a binary logit regression model was applied to estimate the probability of composting adoption based on survey data from smallholder farmers. The results indicate that composting knowledge (OR=2.4253) and social influence (OR=1.3028) are the strongest determinants of adoption, followed by farmer’s attitudes (OR=1.1782) and gardening practices (OR=1.1626), all of which positively influence composting behavior. Policy interventions should prioritize knowledge enhancement and community-based diffusion mechanisms, as these factors have the strongest empirical influence on adoption, while integrating composting training into agricultural extension services. This study extends the TPB framework by incorporating context-specific behavioral constructs derived from PCA, including psychological attitudes, social influence, and resource-related constraints influencing adoption decisions. The findings provide evidence-based guidance for designing targeted behavioral and knowledge-driven interventions to improve adoption of sustainable composting practices in rural agricultural systems.